A variety of designs for electronically commutated motors may be distinguished. They can have a different number n of winding strands, n usually being in the range from 1 to 6.
The current pulses that flow in these winding strands during operation are either unidirectional, or are current pulses whose direction is switched over, by means of a so-called “commutation,” twice in the course of one rotor rotation of approximately 360° el.
Because substantial currents can flow in such a motor, an attempt is made to extend the commutation, in the form of a commutation operation, over a certain time span so that during that time span the motor operates with good efficiency, i.e. without losses. This means that it would be desirable for the energy stored in the relevant winding strand, prior to switchover of the current direction, to be utilized as completely as possible for driving the motor.